Web Mapping Illustrated

Name

ESRI ArcInfo Coverage Files

Synopsis

ESRI ArcInfo coverage files are also known simply as coverages and, less commonly, as ADF files.

File listing

Coverages are made up of a set of files within a folder. The folder itself is the coverage name. The files roughly represent different layers, usually representing different types of topology or feature types.

                  > 
                  ls /data/coverage/brazil
    aat.adf  arc.adf  arx.adf  bnd.adf  lab.adf  prj.adf  tic.adf  tol.adf

A folder with the name INFO is also part of the coverage. It sits at the same hierarchical level as the coverage folder itself. Therefore, to copy a coverage (using regular filesystem tools), the coverage folder and the INFO folder must both be copied. The INFO folder holds some catalog information about the coverage:

                  > 
                  ls /data/coverage/info
    arc0000.dat  arc0001.dat  arc0002.dat  arc.dir
    arc0000.nit  arc0001.nit  arc0002.nit

Data access/connection method

• CONNECTIONTYPE OGR must be used. The ability to use coverages isn't built into MapServer.

• The path to the coverage folder name is required.

• The layer number is used to specify what type of features to draw (as per the layer number from ogrinfo, but minus one).

ogrinfo examples

• The directory is the data source.

• Layers are found within the directory.

Here's an example that uses ogrinfo on a coverage directory:

                  > ogrinfo /data/coverage/brazil
    INFO: Open of 'brazil'
    using driver 'AVCBin' successful.
    1: ARC (Line String)
    2: CNT (Point)
    3: LAB (Point)
    4: PAL (Polygon)

Here's an example that uses ogrinfo to examine ...